The present invention relates to an ink-jet type image-forming apparatus which forms images by ejecting ink onto a recording medium.
Ink-jet image-forming apparatuses for printing by ejecting ink onto a recording medium like a recording paper sheet are known as a kind of output apparatus of computers and work stations. A conventional ink-jet type image-forming apparatus is explained by reference to FIG. 33.
FIG. 33 is a perspective view showing an example of conventional ink-jet type image-forming apparatuses.
A plotter 10 has a platen 12 which supports a recording paper sheet (not shown in the drawing) delivered in the direction indicated by the arrow A (delivery direction). Above the platen 12, two guide rails 14a, 14b are provided parallel to the platen 12. A carriage 16 is attached through a slider bearing (not shown in the drawing) to the two guide rails 14a, 14b to be slidable in reciprocation (in the scanning direction perpendicular to the recording sheet delivery direction). The guide rail 14a is fixed to a casing 15.
A printing head 18 is mounted on the carriage 16. Plural ink ejection outlets (not shown in the drawing) are formed on the ink ejection face (not shown in the drawing) of the printing head 16. Five ink cartridges 18K, 18K (black), 18C (cyan), 18M (magenta), and 18Y (yellow) are provided demountably on the printing head 18.
With the printing head placed above the platen 12, the ink ejection face of the printing head 18 fronts the image formation zone. The inks are ejected through the ink ejection outlets at a prescribed timing to form a band portion of an image. Then the recording sheet is delivered by one printing band breadth by pinch rollers 22 held by holding arms 20 and delivery rollers 24. Again with reciprocating movement of the carriage 16 in the arrow B direction (main scanning direction), the inks are ejected through the ink ejection outlets in accordance with image signals to form image on the new portion of the image formation area of the recording sheet. This operation is repeated to form the entire image on the recording sheet. The printed portion of the recording sheet is guided outside by a sheet discharge guide 26.
In the formation of an image on the recording sheet, the amount of the inks ejected onto the unit area of the recording sheet varies depending on the kind of the image. For example, in formation of a drawing, the amount of the ink per unit area is less since straight lines and curved lines are printed mainly. On the other hand, there are cases where a larger amount of ink is used per unit area. Such cases of a larger amount of the ink application is explained below by reference to FIGS. 34-36.
FIG. 34 is a perspective view illustrating the waving of the recording sheet. FIG. 35 is a schematic drawing illustrating a rising state of the recording sheet in positional relation with the printing head. FIG. 36 is a perspective view illustrating the occurrence of the waviness at the edge portion in the breath direction of the recording sheet. In these drawings, the same symbols are used for corresponding constitutional elements as in FIG. 33.
When a large amount of the ink is ejected per unit area of the recording sheet 30, waviness 32 of the recording sheet 30 occurs as shown in FIG. 34. The waviness 32 forms crest portions 30a and trough potions 30b in the recording sheet 30. The crest portion 30a rises from the platen 12. On the other hand, the distance between the platen 12 and the printing head 18 is designed to be smaller for improving the image quality (print quality). Therefore, the crest portion 30a of the recording sheet 30 can be higher than the level of the ink ejection face (head face) 18a of the printing head. In such a case, the crest portion 30a may rub the ink ejection face 18a, whereby the crest portion 30a may be smeared or damaged.
The waviness 32 arises usually at the printed portions 34 of the recording sheet 30 onto which ink has been ejected (ink has been absorbed). However, the waviness 32 sometimes spreads upstream against the recording sheet delivery direction. The waviness 32 may further spread upstream beyond the pinch rollers 22.
When the waviness 32 has occurred upstream beyond the image formation zone, the ink ejection at this wavy portion 32 further enlarges the waviness 32 to increase the rise of the crest portion 30a. This augments the liability of smearing and damaging of the crest portion by rubbing with the ink ejection face 18a. The enlargement of the waviness may cause rise of the breadth end portion 30c. This may cause hooking of this end portion 30c by the printing head 18 to tear the recording sheet.
One method for solving this problem is to decrease the amount of one ejection of the ink to a practically acceptable minimum amount. However, this decrease of the amount of the ink ejection may decrease the rate of image formation on the recording sheet 30 (printing speed), or may lower the image density (printing density).
As described above, in formation of an image on the recording paper sheet, ink is ejected onto the recording sheet from the printing head 18 on the carriage 16 reciprocating in the arrow B direction. A portion of the ink ejected from the printing head 18 may be scattered around in a mist state before the ejected ink reaches (deposits on) the recording paper sheet. The scattered ink (mist of ink) can stain the image formation area of the recording sheet. To prevent the staining of the image formation area and periphery thereof by the mist, a sheeting member (not shown in the drawing) is provided slightly upstream in the recording sheet delivery direction. This sheeting member is long and narrow, extending in the arrow B direction, and the recording sheet is delivered through under this sheeting member.
However, the mist can adhere to the sheeting member, and can smudge the hand and clothes of the operator when the operator touches the sheeting member.
The present invention intends to provide an ink-jet type image formation apparatus which does not cause a trouble owing to an ink ejected from a printing head.
A first embodiment of the ink-jet type image-forming apparatus of the present invention for achieving the above object is an image-forming apparatus for forming an image in a portion of an image formation area of a recording medium delivered in a prescribed delivery direction, provided with a recording medium delivery unit, the unit comprising:
(1) a driving roller provided upstream before the image formation zone in the recording medium delivery direction for delivering the recording medium,
(2) a driven roller for holding and delivering the recording medium jointly with the driving roller, and
(3) a rise-suppressing member provided upstream before the image formation zone in the recording medium delivery direction for suppressing rise of the recording medium.
The rise-suppressing member may comprise
(4) an upstream sheet-pressing member provided rollably and nearly coaxially with the driven roller, and
(5) a recording sheet-controlling member provided between the upstream sheet-pressing member and the image formation zone, and extending perpendicular to the recording medium delivery direction.
The recording medium delivery unit may comprise
(6) a touch-controlling means for controlling attach or detach of the driven roller to or from the driving roller, and
(7) the rise-suppressing member may be moved jointly with the touch-controlling means.
(8) The sheet-controlling member may have been treated for water repellence at the portion fronting the image formation zone.
A second embodiment of the ink-jet type image-forming apparatus of the present invention for achieving the above object is provided with a carriage carrying a printing head for ejecting ink, and movable in reciprocation in the prescribed main scanning direction for forming an image on a portion of a recording medium delivered in a prescribed delivery direction in an image formation zone by ejecting an ink from the printing head, the ink-jet type image-forming apparatus comprising:
(9) a rise-suppressing member provided upstream before the image formation zone in the recording medium delivery direction for suppressing rise of the recording medium, and
(10) a cleaning member for cleaning the rise-suppressing member.
The aforementioned ink-jet type image-forming apparatus may comprise:
(11) a driving roller which is placed upstream before the image formation zone in the sheet delivery direction and delivers the recording medium in the delivery direction,
(12) a driven roller which is driven by the driving roller and delivers the recording sheet by catching the recording sheet jointly with the driving roller, and
(13) the rise-suppressing member is placed between the driving roller and the image formation zone, and may have a bar-shaped sheet-controlling member extending in an auxiliary scanning direction nearly perpendicular to the aforementioned scanning direction.
(14) The sheet-controlling member may be made of an electric insulating material.
(15) The sheet-controlling means may be electrically chargeable in a polarity opposite to the polarity of the ink ejected from the printing head.
(16) The cleaning member may be made of an electroconductive material and may be grounded.
(17) The cleaning member may be fixed to the printing head or the carriage.
(18) The cleaning member may be rollable freely in contact with the rise-suppressing member.
A third embodiment of the ink-jet type image-forming apparatus of the present invention for achieving the above object is provided with a carriage carrying a printing head for ejecting ink and being movable in reciprocation in the prescribed main scanning direction for forming an image on a portion of a recording medium delivered in a prescribed delivery direction in an image formation zone by ejecting an ink from the printing head, the ink-jet type image-forming apparatus comprising:
(19) a rise-suppressing member for suppressing a rise of the recording medium around the image formation zone, and
(20) a static eliminating member fixed to the printing head or the carriage to discharge firstly the electric charge accumulated in the rise-suppressing member.
A fourth embodiment of the ink-jet type image-forming apparatus of the present invention for achieving the above object is characterized by a cleaning member for cleaning a sheeting member sheeting an area on and around the upstream side beyond the image formation zone in the recording sheet delivery direction in the ink-jet recording apparatus for forming an image by ejecting an ink from a printing head mounted on a carriage reciprocating in a prescribed main scanning direction to form an image on a portion of a recording medium delivered in a prescribed delivery direction and placed in the image formation zone in front of the printing head,
(21) the cleaning member for cleaning the aforementioned sheeting member being fixed at least one of the carriage and the printing head.
(22) The printing head may be demountable from the carriage, and
(23) the cleaning member may be fixed to the printing head.
(24) The cleaning member may have a cleaning roller rollable with the movement of the cleaning member in the main scanning direction.
A fifth embodiment of the ink-jet type image-forming apparatus of the present invention comprises a delivery means for delivering a recording medium in a prescribed delivery direction, and a platen for holding the recording medium being delivered by the delivery means, and forming an image by ejecting an ink onto the recording medium being delivered by the delivery means in the delivery direction onto the platen in an image formation zone,
(25) the image forming apparatus being characterized by a pressing means provided near the image formation zone to press the delivered recording medium against the platen.
(26) The image formation zone is provided downstream after the delivery means in the delivery direction, and
(27) the pressing means may press down, against the platen, the recording medium at the portion ranging from the upstream side before the delivery means to the image formation zone throughout the entire breadth perpendicular to the delivery direction.
(28) The pressing means may be incorporated into the delivery means, and may press or not press the recording medium against the plotter depending on the state of delivery or non-delivery of the recording medium.
(29) The pressing means may be made of a flexible sheet material.
(30) The pressing means may comprise a bar-shaped member placed between the image formation zone and the recording medium delivery means.
(31) The delivery means may pull back the recording medium so as to be sheeted by the pressing means at the downstream end of the recording medium in the delivery direction in a standby state before starting the image formation.
(32) The delivery means may move , in removal of the recording medium at a standby position, the recording medium forward by a prescribed length in the delivery direction to bring the downstream end of the recording medium to be on a downstream side of the pressing means in the delivery direction.
(33) The ink-jet type image forming means may be provided with
(33-1) an openable protecting member for covering the image formation zone and the pressing means, and
(33-2) an opening-closing detection means to emit opening-closing detection signals by detecting the opening-closing state of the protection member, and
(34) the delivery means may deliver the recording medium in accordance with the opening-closing signals from the aforementioned opening-closing detection means.